1. Field of Invention
The present invention relates to image display devices. More particularly, the invention relates to an image display device which is provided with multiple light sources emitting different colors to display color images in a color sequential display method.
2. Description of the Related Art
Conventionally, a color sequential display method of displaying primary color images in sequence, has been used as a method for displaying color images. In this method, when red, green and blue are used as primary colors, for example, a color image having red, green and blue as the primary colors can be displayed by separating a single color image into red, green and blue images and displaying the three color images in sequence. One of the examples of an image display device using such a display method is a projector with a DMD (Digital Micromilior Device) being an optical modulation element having a micro mirror array.
As a light source, a conventional projector often employs an extra-high pressure mercury lamp which emits only white light. However, since the DMD is an element for a time-division display, it is necessary to separate the white light into three primary colors: red, green and blue. A color wheel is typically used to separate light. A color wheel 200 shown in FIG. 6 has three dicbroic filters formed on a glass substrate, and thus has a red transmissive segment (R) 201, a green transmissive segment (G) 202 and a blue transmissive segment (B) 203 configured to transmit single-color light beams, that is, red, green and blue light beams, respectively. The white light can be temporally separated into the three colors by causing a motor to rotate the color wheel 200.
To improve the brightness of a color image displayed by the color sequential display method, the display period of a white image may be provided in addition to the display periods of the primary color images. In addition to the configuration of the color wheel 200 shown in FIG. 6, the color wheel shown in FIG. 7 has a white transmissive segment (W) 204, namely a clear segment, which transmits the white light. A brighter image can be obtained such as when a white image is displayed using such a color wheel. (For example, see Patent Document 1)    [Patent Document 1] JP-A 05-273673